1. Field of the Invention
The present invention is directed to a single layer sound absorption panel of the type which can be used in a sound barrier wall adjacent a highway or other noise source.
2. Background of the Related Art
U.S. Pat. No. 4,325,457 discloses an acoustical barrier formed of two concrete layers joined as a laminate. According to this U.S. Patent, a single concrete layer panel provides inferior results as compared to a two layer panel, and so it provides a first concrete layer comprising mineralized fibrous material blended with cement, and a second concrete layer comprising a fine aggregate concrete. The resulting panel has a thickness of 10 cm and a density of approximately 20 lbs/ft.sup.2, and provides a noise reduction coefficient of about 0.72.
Applicants have previously invented a free aggregate of wood pinchips, and a process for forming the free aggregate, as disclosed in their U.S. Pat. No. 5,019,170, which is hereby incorporated by reference into the present application. The disclosed process, known as the K-X treatment, mineralizes organic fibrous materials by encasing the individual chips in a kaolin mineralizing coating to a degree sufficient to seal in water soluble organic matter held in pores of the chips to prevent the leaching thereof, while maintaining the individual chips in a free aggregate form. The resulting free aggregate can then be mixed with Portland cement to form lightweight "wood concrete".